This invention relates to prosthetic devices for surgical implantation in a human body and is particularly directed to a thumb joint prosthesis for replacement of the carpal-metacarpal thumb joint.
Prosthetic devices for replacement of many parts of the human body have been developed in recent years. The development of any prosthetic device presents numerous problems and it will be apparent that prosthetic devices for replacing joints present unique difficulty since joints must be capable of movement and, preferably, should simulate as closely as possible the movement of the joint which the device is designed to replace.
While most human joints flex in only one plane, a few joints, such as the hip, shoulder and the carpal-metacarpal thumb joint are movable throughout substantially an entire hemisphere. Obviously, creating prostheses for these joints is especially difficult.
Several attempts have been made to provide carpal-metacarpal thumb joint prosthesis. However, none of the prior art devices have been entirely satisfactory. Some of the prior art devices have been extremely complex and, hence, would be very expensive to produce and may be highly subject to failure. Other prior art devices have been unduly bulky and, thus, would be difficult or impossible to implant. Still other prior art devices have provided only very limited movement and, consequently, do not provide adequate replacements for the original joint. A number of relevant patents have been found in the U.S. Patent Office and are listed below:
______________________________________ U.S. PAT. NO. INVENTOR ISSUE DATE ______________________________________ 2,422,302 B. Horn Jun. 17, 1947 3,694,821 W. D. Mortiz Oct. 3, 1972 4,059,854 G. R. Laure Nov. 29, 1977 4,106,128 A. S. Greenwald et al Aug. 15, 1978 4,180,871 R. S. Hamas Jan. 1, 1980 4,213,208 S. Marne Jul. 22, 1980 4,321,121 F. M. Lewis Nov. 4, 1980 4,259,752 J. Taleisnik Apr. 7, 1981 4,276,660 G. R. Laure Jul. 7, 1981 4,304,011 E. J. Whelan III Dec. 8, 1981 4,352,212 D. J. Greene et al Oct. 5, 1982 4,636,218 I. Fukuura et al Jan. 13, 1988 ______________________________________
Described below are some of the more pertinent patents. Reference numbers used below pertain to the disclosures of the described patents.
The patent to Greene et al, Pat. No. 4,352,212, discloses a carpal-phalangeal joint prosthesis consisting of a plastic metacarpal intramedullary plug 3, a metacarpal component 5 consisting of a housing member 6, a plastic bearing insert 7, a metal phalangeal component 9 and a plastic phalangeal intramedullary plug 11. However, the phalangeal component 9 can only rotate in two planes due to its geometry.
The patent to Whelan III, Pat. No. 4,304,011, discloses a phalangeal joint prosthesis having a proximal component 12 consisting of a proximal capsule 22 formed from silicon rubber and a proximal core member 24 formed of stainless alloy with the core being substantially enclosed in the proximal capsule 22. The proximal component 12 additionally includes a bearing cup 28 formed of polyethylene and received in a cup-like socket 31. The cup-like socket 31 is unitarily attached to the large end of the tapered stem 32 of the proximal metal core member 24. However, the outer surface of the polyethylene bearing cup 28 is provided with a protruding retaining flange 34 which is matedly received in a groove 36 in the interior of the surface of the cup socket 31.
The patent to Greenwald et al, Pat. No. 4,106,128, discloses a radial component 10, a concavo-convex socket component 20 and a metacarpal component 30. The radial component 10 comprises a radial intramedullary stem 11 integral with a radial cup 13. The interior surface 14 of the cup 13 is generally concave. The concavo-convex component 20 has a convex surface 21 which mates with the concave surface 14 of cup 13. The socket is made of a compatible plastic, such as a high density polyethylene.
The patent to Fukuura et al, Pat. No. 4,636,218, is directed to a ball-and-socket prosthetic joint, but is intended as a hip replacement and shows that each of the members is threadedly coupled to the bone tissue. However, these threads or grooves are used to enhance adhesive bodies and are not used as the method of fixation in themselves. Also, the Fukuura device has no polyethylene insert.
The remaining patents listed are of general interest only. Thus, those prior art prosthesis are not any more relevant to the present invention.